1. Technical Field
The present invention generally relates to devices for manufacturing lenses. More particularly, the present invention relates to automated machines for applying coatings to lens surfaces.
2. Related Art
Conventional lenses such as those utilized in eyeglasses are often fabricated from materials such as plastic, polycarbonate, and Trivex®, and less commonly from glass. As will be appreciated, a wide variety of materials are being utilized for a wide range of needs, each material having respective advantages and disadvantages. One common characteristic desired in all lenses is the ability to resist scratches and other light impact, and is most often achieved by the well recognized methods of applying hard coatings on the lens. Scratch resistance is not the only generally desirable lens characteristic, however, and other common features include Ultraviolet (UV) ray blocking properties, anti-reflective properties, and mirrored finishes. Many of these features are imparted on lenses by way of coatings applied thereon.
Prior to the development of automated machines, the coating was applied manually, wherein the lens was dipped into a coating resin and subsequently cured in an oven. In further detail, the lens was inserted into a washing chamber to be washed by hand or by the use of a high pressure wash pump. The lens was dried by holding the lens over a filtered compressed air jet, and then the dried lens was manually moved to a coating apparatus. After dipping the lens in the coating apparatus, the coated lens was manually transferred to a curing oven, and the coating was cured. There were substantial deficiencies with this method, namely, the inherent likelihood of human error potentially resulting in the lens surface being unevenly coated, causing optical distortion. In addition to distortion, improperly applied coatings can also result in reduced scratch resistance on the lens surface. The process was expensive and time consuming since the curing process required several hours. Most often the coating material was not recycled, resulting in wasted coating material and a greater volume of hazardous waste requiring disposal. Additionally, substantial environmental controls were necessary to prevent the introduction of dust and other particles that could attach to the surface of the coating, and to prevent the lingering and possible escape of the hazardous coating materials.
Recognizing these deficiencies, those in the art developed a wide variety of machinery to automate the process. Earlier machines were often large and cumbersome, as well as expensive, often precluding eyeglass retailers from procuring such machinery. Retailers were thus required to send the lenses to larger manufacturing facilities, resulting in greater costs and longer lead times for customers. Conventional lens coating machinery generally divided the process into the washing/drying stage, coating stage, and the curing stage. In the typical washing/drying stage, the lens was placed in a basin and sprayed with a jet of de-ionized water, and dried by evacuating the basin. In order to enhance drying, the lens was spun to remove the water by centrifugal force. In the coating stage, a process known in the art as spin coating was utilized. First, the coating material, typically a volatile solvent, is deposited on the surface of the lens in excess of the actual volume required. The lens is then rotated at great speeds, spreading the coating material evenly across the surface of the lens and forcing the excess off the edge of the lens. As the lens is rotated at a constant speed, evaporation of the solvent is facilitated. After a thin film of the coating material is deposited, the lens is dried and the coating thereon is cured in an ultraviolet oven, resulting in a completed lens.
While the basic process of cleaning, drying, coating, and curing remained the same in the lens coating machines, a number of improvements were made which were intended to overcome the above described limitations of size and cost. Nevertheless, deficiencies persisted in areas such as process throughput, energy efficiency, and device lifespan. Thus, a lens coating apparatus which can overcome these limitations is needed in the art.